#4547: When debugging a very large function, it was not always

possible to update the lineno attribute of the current frame.

Lib/test/test_trace.py

@@ -740,6 +740,23 @@ class JumpTestCase(unittest.TestCase):
     def test_19_no_jump_without_trace_function(self):
         no_jump_without_trace_function()
 
+    def test_20_large_function(self):
+        d = {}
+        exec("""def f(output):        # line 0
+            x = 0                     # line 1
+            y = 1                     # line 2
+            '''                       # line 3
+            %s                        # lines 4-1004
+            '''                       # line 1005
+            x += 1                    # line 1006
+            output.append(x)          # line 1007
+            return""" % ('\n' * 1000,), d)
+        f = d['f']
+
+        f.jump = (2, 1007)
+        f.output = [0]
+        self.run_test(f)
+
     def test_jump_to_firstlineno(self):
         # This tests that PDB can jump back to the first line in a
         # file.  See issue #1689458.  It can only be triggered in a

Misc/NEWS

@@ -12,6 +12,9 @@ What's New in Python 2.7 alpha 1
 Core and Builtins
 -----------------
 
+- Issue #4547: When debugging a very large function, it was not always
+  possible to update the lineno attribute of the current frame.
+
 - Issue #5330: C functions called with keyword arguments were not reported by
   the various profiling modules (profile, cProfile). Patch by Hagen Fürstenau.
 

Objects/frameobject.c

@@ -98,7 +98,7 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno)
 	int new_iblock = 0;		/* The new value of f_iblock */
 	unsigned char *code = NULL;	/* The bytecode for the frame... */
 	Py_ssize_t code_len = 0;	/* ...and its length */
-	char *lnotab = NULL;		/* Iterating over co_lnotab */
+	unsigned char *lnotab = NULL;	/* Iterating over co_lnotab */
 	Py_ssize_t lnotab_len = 0;	/* (ditto) */
 	int offset = 0;			/* (ditto) */
 	int line = 0;			/* (ditto) */
@@ -148,7 +148,7 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno)
 		/* Find the bytecode offset for the start of the given
 		 * line, or the first code-owning line after it. */
 		PyString_AsStringAndSize(f->f_code->co_lnotab,
-					 &lnotab, &lnotab_len);
+					 &(char*)lnotab, &lnotab_len);
 		addr = 0;
 		line = f->f_code->co_firstlineno;
 		new_lasti = -1;